Aircraft trainer for aerial gunners



R. c. DEHMEL 2,471,315

AIRCRAFT TRAINER FOR AERIAL GUNNERS May 24, 1949.

Filed Feb. 3, 1944 6 Sheets-Sheet 2v HORIZON BAR F/G. asl/Pur nam/cna new? sax M v TRAINER NO. l.

/A/vE/V To@ RCDEHMEL A T TOR/VE V 23 T5 6 moss REFERENCE- SEARCH RDW May 24, 1 949.v f R, C, DEHMEL 2,471,315

l AIRCRAFT -TRAINER FOR AERIAL GUNNERS Filed Feb. 3, 19144 6 Shebs-Sheet 5 OUTPUT /N VEN To@ R. C. DE HME L A T TORNE Y @mw-MCE 'SEARCH Rum R. c. DEHMEL AIRCRAFT. TRAINER FOR AERIAL GUNNERS May 24, 1 949.

6 Sheets-Sheet 4 Enea Fab. s, 1944 NKY /Nz/ENTOR RC DEHMEL ATTORNEY May 21g-1R49..

Filed Feb. s, i944 F/G. z

TRA/NEAR N0. l.

TRA/NER N0. 2

mss RRRRRRRCE SRRRCR ROOR R. c.' DEHMAEL 2,471,315

AIRCRAFT TRAINER FOR AERIAL GNNER e sheets-sheet 5 GEAR BOX REDUCTION GEAR 50X /NL/EN TOR RCDEHMEL May 24, 1949. R.' c. DEHMEL AIRCRAFT TRAINER FOR- AERIAL GUNNERS 6 Sheets-Sheet 6 Filed Feb. 3, 1944 hwg/wo@ R. @DEH/WEL A 7' TORNEI Patented May 24, 1949 UNITED (STATES PATENT OFFICE AIRCRAFT TRAINER FOR AERIAL GUNNERS I .Richard:C. Dehmel,-Summit, N. J., assignor to Bell Telephone Laboratories, Incorporated, New .York, N. Y., acorporation of .New York Applicationr-February 3, 194.4,l Serial No.520,912

l1 This invention rel-ates:.to aircraft training apparatus and more .particularly tc apparatus applicable thereto for enabling vthe 4.training of .a pilot -or gunner in .aircraft .gunnery Radio equipmenthas.been'developed .Whichldi- .5

rectively radiates .high frequency impulses and -measures the strength .and time .delay of italics.A

which are reilected back from interposed objects. When such equipmentfis used inairplanes its antennae :or radiators are .directively oscillated to `vscan .a wide anglereld .ahead -of the airplane. vThrough.synchronized circuits the reflected Waves fform images on oscilloscope screens which have `intensities and coordinate '.positionsvcorresponding .to the degree of reflection and location of the .object .scanned by the tramsrnittedybeam. Since -only relatively .dense objects Iproduce images the equipment is particularly effective in showing .the location of --ships or in spotting other airplanes .ithrough clouds -cr darkness. {The-.time of delay between the transmission of any impulse and the reception -of the returning wave is a measure of :the distance A-i-rom vthe transmitter 'to the reflecting object. Thismay 'be indicated on one oscilloscope screen serving -as,;a. range oscilloscope 4and :the coordinate posi-tion of theobject vwith rev.spect -to the transmitter maybe indicated on .a .Bene-nd oscilloscope screenserving as alocation oscilloscope The use of equipment of-this type .is lhighly fimportant inmilitary operations since -itmay be employed to locate enemy -aircraft at lnight or through clouds, to locate enemy ships, .to locate .aircraft carriers lostbypilots inovercastsat sea or .to direct gunnery or bombing. commercially -this equipment will become important to trans- -port -pilots as a mean-s for detecting the presence of .other airplanes on airways .and as an aid tol landing. Like other navigation aids-experience required in the operation of the equipment to `acquire efliciency in its use. However, ltoavoid loss-of time, the hazards .and the expense of training with actual service equipment, it is de- -sirable that equipment may be available to enable the aircraft .operating personnel to be .taught lon -the :ground to fly airplanes by instruments and 4to coordinate the iiight with information received by the radio equipment.

It is therefore the object of the present invention to simulate in ,an aircraft trainer the reception which would `4be attained s.on actual radio direction and-range fin-ding equipment.

.A'feature .of the `invention is the provision .of :equipment for securing the instant coordinate locations of thetraiiner and an assumed target,

.which may be a second trainer or anassumed xed objective simulating, for example, a ship at sea level, vand combining such coordinates to .secure the azimuth and elevation angles of the :Hight vpath which should 'be flown by the trainee l:to reach the objective or target, or which would v.cause a gun if carried by the trainerto beproprerly trained With respect to the target and to A:secure the distance or slant range from the trainer 1.0 to the objective or target.

,Another feature of the invention is the provision of equipment whereby the securing of .the .azimuth and elevation angles vof the flight path 21R-2W .be caused -to `operate a location indicator ,154:0 lproduce an image on 4its .screen representing the location of the distant objective or targetv .with respect -to the trainer toward which the vtraineright should bear.

Another feature of .the invention is the pro- .;U -.vision of apparatus whereby the imageis displaced on lthe screen in accordance with the .simulation in the trainer -oi any pitch, .bank or l,turning movements during the simulated flight.

Another feature of the invention is the provig-.sion .of equipment whereby the .distance or slant range measurement from the trainer to the .ob-

jective or target, as secured by combining the coordinate locations of the trainer ,and target, islutilized to voperate a range oscilloscope or indi- ;U cator .of range to produce `an image at a scale point on its screen indicative o such distance `orslant range.

,A .further feature of the invention isthe pro- ,vision of a key simulating a gun firing key which 35 vis Leffective .only when .the target is at the proper position .on the screen of the location oscilloscope, to correspond to the lead at which a gun would be .accurately trained on the target, to ,cause the target .simulating .images v.appearing on thescreenso the .Oscilloscopes to become `re- .spectivelydepressed and dark thereby .simulating ythe target as hit4 and sinking or falling .and with a ,changed range.

v ;[n accordance with one embodiment .ofthe 45 present invention, .potentiometers which are con- ,trolled by thecourse .charting apparatus of .an air- .crat trainer .anda potentiometer controlled by .the altimeterdriving motor of the trainer are provided to apply potentials to three summing @ampli-fiers which potentials .haveinstant -values proportional to the x1, u1-.and .ziCairtesianlcol ...ordinates of the-position yof the ltrainenwith re- -spect to a reterence point on the-terrain map .over which the simulated flight is xbeing made.

..55 iat-the same time similar equipment at the ebjec- 3 tive or target which may, for example, be another trainer, applies potentials to the three summing amplifiers lwhich potentials have instant values proportional to the x2, y: and z2 Cartesian coordinates of the position of the objective with respect to the same reference point on the terrain map.

The summing amplifiers combine these potentials and from the results determine potentials which are proportional to the x, y and e Cartesian coordinates of the flight path from the first trainer to the objective or target. Since polar coordinates are better adapted than rectangular coordinates to the control of instruspace, these coordinate potentials are electrically converted into polar coordinate potentials indicative of the range r, the azimuth angle a and the elevation angle e, defining the length and direction of the night path over which the trainer should be flown to reach the target or to cause a gun if carried by the trainer to be properly trained with respect to the target and to secure the range from the trainer to the target.

The range potential thus secured is used to control an oscilloscope to produce an image at a scale point on its screen indicative of the range or distance from the trainer to the targetorto operate a voltmeter type of indicator the pointer of which is deflectable in accordance with the range.

The azimuth angle a and the elevation angle e potentials are utilized to control the operation of servo-motors which rotate the brushes of potentiometers carried by their shafts through angular positions proportional to the values of the a and e potentials and thus, with the potentiometer windings connected to sources of direct current, to produce potentials between the brushes of each potentiometer proportional respectively to the a and e angles. These potentials may then be applied across the horizontal and Vertical plates of an oscilloscope to position an image representing the target which is indicative of the position of the target with respect to the position of the trainer, assumed to be at the intersection of the cross hairs of the oscilloscope screen.

However, the instant attitude of the trainer, that is, whether it is simulating the yawing movement of an airplane about its vertical axis in response to steering, whether it is simulating the rotational movement of an airplane about its lateral axis in a pitching movement which may be due to either climbing or diving, and whether it is simulating the rolling movement of an airplane about its longitudinal axis which would occur in banking, inuences the position of the image of the target as it appears on the screen of the location oscilloscope. The simulation of the yawing movement appears as a i change in the indications of the compass and turn indicator of the trainer and by the movement of the course charting apparatus, the simulation of the pitching movement appears as a raising or lowering of the horizon bar of the artificial horizon instrument and the operation of the altimeter and the simulation of the rolling movement appears as a change in the slope of the horizon bar of the artificial horizon instrument. Therefore, to introduce corrections for these movements, the winding of the a angle potentiometer is mounted for rotation by the steering motor of the trainer which responds to the steering control exercised by the trainee, and as a consequence of the rotation of the brushes in ment-s for indicating a location and range in v e proportion to the a angle and the rotation of the winding in proportion to the steering or heading angle a corrected azimuth angle potential a iis produced. Similarly the winding of the e angle potentiometer is mounted for rotation by the motor which controls the horizon bar of the artificial horizon instrument of the trainer in response to the operation of the elevator control of the trainer for climbing or diving and, as a consequence of the rotation of the brushes in proportion to the e angle and the rotation of the Winding in proportion to the climbing or diving angle which may be 'designated w, a corrected elevation angle potential sie is produced. These potentials are applied to the opposite points of two sine-cosine potentiometers, the sine and cosine brushes of which are mounted on a shaft driven by the motor which controls the tipping of the horizon bar of the artificial horizon instrument to indicate the angle of roll. The sine and cosine potentials derived from the potentiometers are then applied to summing ampliers the output potentials of which have values proportional to the corrected ac and ec location angles of the target with respect to the trainer. These potentials are then applied across the horizontal and vertical plates of the location oscilloscope.

From an observation of the position of the target image on the screen of the location oscilloscope the trainee may control the trainer until the image coincides with the intersection point of the cross hairs of the screen at which time the simulated flight path will be in exact coincidence with the path from the trainer to the target. This would be the correct instant'for the firing of a gun to score a hit on the target except for the necessary lead.

To simulate gunn'ery a gun firing or trigger release key and three relays are provided. Two of these relays are of the voltmeter type. One of them has its winding connected across the horizontal plates of the location oscilloscope and is designed so that its vane is positioned midway between its contacts and out of engagement therewith when the potential across its winding is equal to the potentials required to center the image' horizontally on the oscilloscope screen. The other of the voltzneter relays has its winding connected across the vertical plates of the location oscilloscope and is designed so that its vane is positioned midway between its contacts and out of engagement therewith when the potential across its winding is equal to the potential required to center the target image vertically on the screen. The third relay is normally held operated over the normally closed contacts of the trigger release key and is also held operated over contacts of either or both of the voltmeter relays if the potentials applied across the plates of the oscilloscope are not such as to center the target image on the screen. Hence if the image is exactly centered on the screen, which is the position when guns would be pointed directly at the target the third relay is held operated only by the trigger release key, If at this instant the key is operated the third relay releases and changes the output potential from one summing amplier to alter the coordinate potential z which in turn causes the resetting of the servornotors for a new value of the elevation angle E and causes a new value of the polar coordinate indication of the slant range T. With these values changed the position of the image of the target on the screen of the location oscilloscope is depressed to show that the target has been hit and todepict it as falling to the ground and the setting of the range indicator is changed to show the change in range.

-In lieu of equipment being used to simulate two airplanes in ight, fixed potentials may be introduced at the summing amplifiers instead of the variable potentials x2, y2, ez supplied by the second trainer and thereby simulate stationary objects in the air or on the ground, or the potentials rc2, y2 may be varied and the potential ez made zero to simulate a ship at sea or an object moving on the ground.

`In accordance with afurther embodiment of the-invention, a rst trainer is provided with a potentiometer which is controlled by a motor of fthe trainer operative in accordance with the air speed of the simulated ight, which potentiometer applies a potential Varying in accordance with the simulated air speed upon a second sine-cosine potentiometer whose brushes are driven by the motor of the trainer operative toraise or lower the horizon bar of the artificial horizon instrument of the trainer to indicate the climb-or diving movement of the simulated iiight, from which potentiometer potentials are derived which have instant values proportional to tf1- As'zoand horizontal projection Cartesian (Ash) coordinates of the position of the trainer with respect to a reference point on the terrain map over which the simulated flight is being made. The horizontal projection potential Ash is further applied to a third potentiometer, the brushes of which are controlled by a motor operative in accordance with the compass heading of the simulated night from which potentiometer potentials are derived which have instant values proportional to the Asma and Asyo Cartesian coordinates of the position of the trainer with respect to a reference point on the terrain map over which the simulated iiight is being made. rThe Asma, Asyo and Asso potentials are then impressed upon three amplifiers, thev output circuits of which are connected respectively to the control phase stator windings of the two-phase motors of three motor generator assemblies. The Xed phase stator windings of the motors and generators Aare energized from a source of steady alternating current potential and the other stator windings of the generators are connected to apply feedback potentials to the associated ampliers whereby the amplifiers are controlled to cause the generators to be driven at speeds which vary linearly with respect to the input potentials.

"The output potentials x1, yi and ai from the generators are also applied to the inputs of three summing amplifiers. At the same time similar equipment of a second trainer applies potentials to the three summing ampliers which potentials have instant values proportional to the m2, y2 and 22 Cartesian coordinates of the position of the second trainer with respect to the same reference point on the terrain map. The summing ampliners combine these potentials and from the results determine potentials which are proportional `to the m, 1/ and z Cartesian coordinates of the flight path between the two trainers. These coordinate potentials are then electrically converted into polar coordinates which are indicative of the range r, the azimuth angle and the elevation angle e defining the length and direction of the flight path over which either trainershould be own to reach the other trainer or to cause a gun if carried by `either trainer to be .properly trained with respect to the other trainer fil) A.. ai)

A 6 and to secure thedistance or range between the trainers.

The range potential thus derived is used to control indicating instruments associated with the respective trainers to produce scale readings indicative of the range or distance between the trainers. The azimuth angle potential a thus derived is used to drive a servo-motor which rotates one input shaft of each of two differential gear boxes allocated respectively tothe two trainers.

The other input shafts of the two gear boxes are driven by the motors which drive the Compasses of the two trainers. gear boxes are connected to the brush shafts of potentiometers whereby, with the servo-motor driven input shafts of the gear boxes oriented degrees apart in rotational spacing, the brushes of t1 e two potentiometers are so driven that the potentials derived from the windings of such potentiometers vary in accordance with the a angle as rnodiiedby the instant value of the heading or compass angle' or aiii in response to the simulated yar-.fing movement of the rst trainer about its vertical axis and a2i(2+l80) in response to the,simulated yawing movement of the second trainer about its vertical axis.

The elevation angle potential e is used to drive second servo-motor which turns one input shaft of each of two other differential gear boxes allocated respectively to the two trainers. The oth- .t shafts of these gear boxes are driven by the motors which elevate or depress the horizon oars of the artificial horizon instruments of the tf'o trainers. The output shafts of these gear ifomioic'seters whereby, with .the servo-motor driven input shafts of the gear boxes oriented 180 degrees apart in rotational spacing, the brushes of these potentiometers are so driven that the potentials derived from the windings of such pctenticmeters vary in accordance with the e angle modined by the instant value of the climbing or diving angle w or @1to1 in response to the simulated pitching movement of the first trainer about its lateral axis and ezzL-(oz-l-lSiP) in response to the simulatedpitching movement of the second trainer about its lateral axis.

These potentials are applied to the opposite points on the windings of a pair of sine-cosine potentiometers associated with each trainer, the brushes of which potentiometers are mounted on a shaft driven by a motor which controls the tipping of the horizon oai` of the artificial horizon instrument to indicate the angle of roll. The sine and cosine potentials derived from these potentiometers are then' applied to summing amplifiers. the output potentials of which have values proportional to the corrected ac and @c location angles of each trainer with respect to the other trainer. rlhese derived potentials are then utilized to control location indicating Oscilloscopes in the same manner as in the iirst modication.

For a clearer understanding of the invention, reference may be had to the following detailed description thereof. taken in connection with the accompanying drawings in which:

1 shows the course charting apparatus of aircraft trainer and certain of the instrument.

driving shafts of the trainer;

Fig. 2 is a circuit diagram illustrating the application of the invention to a trainer;

Fig. 3 shows the structure of the sine-cosine potentiometers illustrated schematically in Fig. 2;

Fig. 4 is a. diagram illustrating the resolution of The outputshafts of the u boxes are connected to the brush shafts of twov the Cartesian coordinates of a trainer night position and a target position into the polar coordinates of a flight path from the trainer flight position to the target position and the distance or range between the trainer flight position and the target position;

Fig. 5 shows one form of summing amplifier circuit which may be employed in the circuit of Fig. 2;

Figs. 6 and 7 taken together illustrate a modied form of the invention;

Fig. 8 is a side elevational view of the trainer; and

Fig. 9 shows the trainer. s A

The invention is not limited in its application to any particular forro of trainer as it may be used in any type having air speed, climb and turn indicators by the provision of apparatus for converting instrument operations into electrical potentials. For the purposes of illustration the invention has herein been shown as applied to a trainer of the type disclosed in my application 'Serial No. 398,590, nled June 18, 1941, and in Iny Patent No. 2,366,603, granted January 2, 1941. The trainer as disclosed schematically in-Figs 8 and 9 is provided with a pilots station 8dr? laving the usual control stick SGI and rudder pedals, hidden behind the apparatus cabinet S02, and an instrument panel 2563. The instrument panel S03 shown more clearly in Fig. 9 is supported by the instructors table Stil. The panel carries the instruments corresponding to the usual instruments found in an actual airplane which consist of meter 393 depicting airspeed, the combination meter 699 depicting rate oi' turn of the aircraft and ball stability, the meter Slt! depicting rate of climb, the meter Sil depicting altitude, the meter SI2 depicting compass course, the clock SIS, the tachcrneter the control SI5 which simulates the throttle control of the aircraft and the attenuator SI5. driven from the airspee motor 2 through the shaft 8|?, pulleys BIS and @i9 and belt 82D. The gear train B2i is a part oi the mechanical connection between the steering motor 3i which is housed within the casing S22 secured to the back of panel t and the drf ing head 26 of the course charting pantograph 3%. rEhe rate of climb meter SIS and aitirneter GIS are driven through gear train 8253 from the shaft of altimeter motor also housed within the casing 822. The panel S93 in addition carries a target oscilloscope OSCI and a range meter such as RI to assist the student pilot in gunnery practice. A course charting apparatus co5 is supported. on the top of the table and is responsive to the operation of the control stick. This trainer, as illustrated in Fig. 1, has a course charting device 5&25 of the pantograph type. The main pantograph comprises iour arms I, 2, 3 and -l pivoted together at their junctions by pit-ots G, i and 8. The arras I and 2 have short extensions 9 and lil, to the ends of which pantograph arrns il and I2 are pivoted, the latter arins being pivoted together at their junction by a pin I3. Also pivoted to the arrns I and 2 by pivots I5 and I5 are two additional pantograph arnis I5 and Il pivoted t0- gether at I3 and carrying a scriber for marking the ight course on the terrain inap or record sheet I9. At the junction point S is located a driving head 28 of the type fully disclosed in my application Serial No. 398,590, above referred to, having therein a tractor wheel 31, shown in Fig. 8, driven by the sprocket Wheel 2I and through instrument panel of thel rThe airspeed meter 888 is l -ediy attached to the slider 32, engages.

8 the sprocket chain 22 by the driving sprocket Wheel 23 which is secured to the upper end of the pivot shaft 5. rJhis shaft is mounted for rotation in a bearing secured to the table 23 and is driven a iff-.form gear 25 in turn driven by the Worm 26 mounted on the shaft of the motor 21. To guide the chain 22, idler pulleys 38, 35 and 40 are rotatably mounted on the pivots E, 'I and I4 of the pantograph.

rEhe tractor wheei Sl is pivoted on a horizontally disposed axle which is rotatably supported in the lower end of the driving head 2i), which head is rotatable about its vertical axis to orient the tractor Wheel in response to the operation of the trainer control in the simulation of steering. To rotate the driving head the sprocket wheel 28 is attached thereto, as fully disclosed in my application Serial No. l398,590, hereinbefcre referred to, which is driven by a sprocket chain 29, driven by a driving sprocket wheel 30 mounted to rotate freely With respect to the pivot shaft 5 and in turn driven through bevel gearing by the steering motor 3| or the trainer. To guide the chain 23, idler pulleys 3?, 56, 55B and i8 are rotatably nlounted on the pivots 5, 7, Id and l5 of the 'pantograpn xlhus through the operation of motor 2l, the driving head 2@ is advanced over the surface oi the table at a speed proportional to the indicated air speed and is oriented to dete'rnine the direc-*ion of its movement under the co trol ci motor 2i and, because of the pantograph construction, the scriber carried at the pivot pointV E3 marks the course on the map or record i t. The pivot pin I3 also moves through a path which corresponds to and is parallel to the flight course traced by the scriber. For the purposes of the present invention the movement of the pin i3 is utilised to control potentiometers to determine potentials indicative o the degree and direction of the movement of the scriber with respect to the terrain inap i9 and which potentials `may be used to indicate the instant position of the scriber or the flight position of the trainer in its simulated flight with respect to a reference line assumed to be a line parallel to the lower edge of the mais IQ as viewed in Fig. 1. To accomplish this the pivot pin I3 is engaged with a slider 32 which is supported on and slidable along the arin 33 secured t0 the shaft 34. Carried by the arm 33 is a potentiometer winding 35 with one edge oi which the brush 36, insulat- As the slider moves toward and away from the shaft more or less of the turns of the potentiometer winding 35 are made effective.

Movement of the pin I3 about the shaft 5 also causes, o. rotational movement of the shaft 34. This rotational movement of shaft 3ft is employed to control a potentiometer of the type disclosed in Fig. 3. This potentiometer has two windings 33' and 33 varying in resistance along their cards in accordance with sine wave functions. The insulation is removed from the wire at the upper s" `aight edges of the cards and two brushes 39 and insulatedly mounted on the shaft 4l, are provided for engagement therewith. These brushes are positioned 9-0 degrees apart and With a potential applied across the terminals 112 and at the junction points of the windings, the potential at the point of engagement of one brush with a winding will vary in accordance With the sine of the angle which that brush makes with the terminal position 42 and the potential at the point of engagement of the other brush with a 9 winding will vary in accordance with the cosine of the angle.

Since the movement of the pantograph of the course charting apparatus is thus converted into an angular movement oi shaft 35, and thus of the brushes of a sine-cosine potentiometer carried by such shaft, and into a linear movement of the brush 3S with respect to the potentiometer winding 35, these potentiometers may be employed to determine the instant location of the scriber with respect to the and y coordinates of the terrain map and thus the position of the trainer in its simulated flight. v i

Referring now to Fig.,2, it will be assumed that two trainers are to be employed for the purpose oftraining aircraft personnel in the use of radio locating equipment and that the rst trainer identified as trainer No. 1 is equipped with the training equipment disclosed in this figure with the exception of thi` apj'aratus disclosed within the dot-dash lines in the upper' right portion of the figure and that this latter apparatus represents the course charting equipment of the second trainer No. 2 `employed as a target or objective for the iirst trainer. The winding 35 of the potentiometer P! of the first trainer is connected to the left secondary winding of the transformen T. the primary winding of which is connected to a source of alternating current. The brush 351 of this potentiometer is connected to the primary winding of transformer TI and the end terminals of the secondary winding of the latter transformer are connected to the junction points between the windings of the sine-cosine potentiometer P2. The mid-point of the secondary winding of transformer TI and the mid-points of the windings of the potentiometer P2 are connected to ground. With the windings of transformer Tl wound for unity transformation, the potential r1, derived by the position of brush 351 of poteniometer Pl is applied to produce potentials of equal magnitude and opposite polarities at the junction points of the windings of potentiometer P2 for exciting such windings. It is to be noted that the position of the brush 361 of potentiometer Pl and the angle c1 between the brush 2G01 of potentiometer P2 and the y axis of such potentiorneter determine the ight position of the No.. l trainer with respect to the horizontal plottingv surface of the terrain map. To fully determine the flight position of the No. 1 trainer, a third potentiometer P3 is provided7 the winding of which is energized by potential applied through 'the left secondary winding of transformer T and the brush of which is driven from the shaft which drives the altimeter of the trainer. This potentiometer therefore produces a potential at its brush which is proportional to the e coordinate of the night position of the trainer and may be expressed as ei.

Since the potentiometer Pl produces a potential 1'1 proportional to the radial distance of `the slider brush 35i from the shaft 341 and this potential is fractionated by the sine-cosine potentiometer P2 in accordance with the angular position on of the arm carrying the potentiometer Pl, the potentials resulting at the points of engagement of the brushes Zii and 20h of the potentiometer P2 with the windings thereof are proportional to the :r and y coordinates of the flight position of the No. l trainer and may be expressed as l assumed to be conducting a simulated :flight over is opposite to that of ai.

10 Similarlywith respect to the No. 2 trainer,

the same terrain and serving as a target or objective for the first trainer, the potentiometer P4 thereof supplied with potential from the right secondary winding of transformer T then produces a potential r2 proportional to the radial distance of Athe slider brush 362 from the shaft 342 and this potential is fractionated by the sine-cosine potentiometer P5 in accordance with the angular position a2 oi the arm carrying the potentiometer P4, resulting in the production of potentials at the points of engagement of the brushes 2002 and 2N2 of the potentiometer P5 with the windings thereof which are proportional to the :r and y co ordinates of the night position of such No. 2 trainer and which potentials may be expressed as 12:12 cosine a2 To fully determine the flight position of the No. 2 trainer, the potentiometer P5 is provided therein, the winding of which is energized by potentialvr applied through the right secondary winding of transformer T and the brush of which is driven from the shaft which drives the altimeter of that trainer. This potentiometer therefore produces a potential at its brush which is proportional to the e coordinate of the flight position and may be expressed as a2.

Itwillbe notedthat theleft secondary windingof transformer T which supplies potential to the potentiometer P2 is connected reversely to the right secondary Winding of transformer T which supplies potential to the potentiometer P5 so that the instant value of r2 is opposite in phase to that of r1. Since these secondary windings of transformer T also supply potentials to the potentiometers P3 and PS, the instant value of potential an Hence the resultant potentials from potentiometers P2 and P5 mayA be impressed on the summing amplifiers SAI: and SAQ! and the resultant potentials from the potentiometers P3 and PB may be impressed on the summing amplier SAB to calculate the difference between the flight position of the two trainers in their simulated flights according to the equation:

The summing amplifiers employed, such for example as the amplifiers SAI, SAy and SAZ,v may be of the type disclosed in full lines in Fig. 5. This amplier comprises a first voltage amplifier tube AMP!v upon the control grid of which signal potentials are applied through parallelly connected resistors such as 50| and 582. The amplified output from this tube is applied through the coupling resistor 5*-33 upon the control grid of a second amplifier tube AMP2, the amplified output from which is applied to the control grid of the detector tube DT through the coupling resistor 534. The output circuit of the detector tube is connected to the output terminals 585 and SBS. The amplifier is stabilized by a negative feedback circuit from the anode of tube DT through resistor 531 to the control grid of the amplifier tube AMPL The' filaments of the tubes are heated from a filament current supply (not shown)4 and control grid, biasing potentials, screen grid potentials and anode potentials are applied to thev tubes from appropriate taps of .p

theA battery 508.

It is important that proper phase relations be maintained throughout the circuit. Should phase shifts occur, for example, in the potentiometer windings due to admittances to ground, these may be adequately corrected in most instances by condensers fill and 45 connected between the sliders or brushes and the high Voltage end of any potentiometer as shown for esample in Fig. 3.

For the purpose of indicating the flight position of the target or objective with respect to the line of simulated flight of the No. 1 trainer and for giving the trainee an indication simulating the distancey or slant range between the flight positions of the two trainers, oscilloscope OSCI and an indicator RI are provided in the No. 1 trainer. The oscilloscope OSCI is arranged to produce a spot of light on its screen simulating the target or objective position which is dependent upon the azimuth and elevation angles between the flight position of the No. 1 trainer and the flight position of the target or objective, in the case assumed, the No. 2 trainer. The range indicator R! is also dependent on the air line distance or range to the target or objective.

.Hence for operating the oscilloscope OSCI and indicator R! it is desirable to express the relative position of the target or object with respect to the No. 1 trainer in polar coordinates, a forthe azimuth angle, e for the elevation angle and r for the slant range rather than in the Cartesian coordinates zr, y and z produced as hereinbefore described by the summing amplifiers.

Referring now to Fig. 4, it will be assumed that at any given instant, the night position of the No. 1 trainer maybe indicated at the point A which is located at the perpendicular distance :r1 from the plane including the lines OY and OZ, at the perpendicular distance y1 from the plane including the lines OX and OZ and at the perpendicular distance ai from the plane including the lines OX and OY. Lines mi, y1 and a1 are therefore the Cartesian coordinates of the position of the point A. It will further be assumed that the flight position of the No. 2

perpendicular distance 12 from the plane including the lines OX and OZ and at the perpendicular distance z2 from the plane including the lines OX and OY. Lines m2, y2 and e2 are therefore the Cartesian coordinates of the position of the point B.

If now a plane be passed through the point A, parallel to the plane of lines OX and OY and the line BC drawn from the point B perpendicular to such plane, it will be seen that the line BC represents az-ei and may be designated e. Ii now the line :ci is extended in this plane to the point D where the line drawn in the plane from the point- C and parallel to the plane through lines OY and OZ intersects the extension of line r1, then AD will represent .r2-:r1 and may be designated :c and CD will represent yz-yl and may be designated y. Thus lines AD, CD and BC represent the Cartesian coordinates cc, y and e of the night path or slant range between the two night positions A and B which coordinates are represented by the output potentials of theI summing amplihers SA, SAy and SAQ. A line drawn in the horizontal plane of the point A to-the point C represents the horizontal range rh between the points A and C and the line connecting the points 12 A and B represents the slant range 1'. The horizontal angle ACD defines the azimuth angle a between the y coordinate CD and the horizontal range AC or rn and the vertical angle BAC defines the elevation angle e between the horizontal range AC or rh and the slant range AB or r.

If now a line be drawn in the horizontal plane through the point A from the point D and perpendicular to the line AC, then the angle CDE is equal to 99 degrees-a, and angle EDA is equal to a. The following equations may now be evolved:

ED=DC sine a=il sine a ED=AD cosine a= cosine a y sine 'a-- cosiney a :r cosine. -y sine a=0 (4)` AE=1r sine a EC=y cosine a :r sine a-i-y. cosine a=AE+EC=AC 1f sine ---y cosine a=rh (5) If a line also be drawn in the vertical plane through the line AC and BC from the point C perpendicular to the line AB, then the angle ACF is equal to 90 degrees 6; and angle BCF is equal to e. The following equations may now be evolved:

FC=AC sine e--rh sine e FC--BC cosine 5:2 cosine e rh sine e=z cosine e rh sine e-e cosine e=0 (6) AF=rh cosine e FB=z sine e e sine e-i-rh cosine E=AF+FB=AB 2 sine e-l-rh cosine e=r (7) To secure solutions for Equations 4 and 5, a pair of sine-cosine potentiometers Pl and P8 is provided, each with its brushes secured to but insulated from a shaft 292. The diametrically opposite junction points between the windings of the potentiometer Pl are connected to the end terminals of the secondary winding of transformer T3, the primary winding of which is connected across the output terminals of the summing amplier SA. The mid-point of the secondary winding og the transformer T3 and the mid-points of the windings of potentiometer P1 are connected to ground. With the windings of transformer T3 wound for unity transformation, the output potential from the amplier, SAI, which is proportional to the :r coordinate, is applied to produce potentials of equal magnitude and opposite polarity at the junction points of the windings of potentiometer Pl. The diametrically opposite junction points between the windings of the potentiometer P8 are connected to the end terminals of the secondary windings of transformer Tt, the primary winding of which is connected across the output terminals of the summing amplifier SAy. The mid-point of the secondary winding of transformer T4 and the mid-points of the windings of potentiometer P8 are connected to ground. With the windings of transformer Til wound for unity transformation. the output potential from the ampli er SAy, which is proportional to the y coordinate, is applied to produce potentials of equal magnitude and opposite polarities at the junction points of the windings of potentiometer P8.

The brushes 235 and 207 of potentiometers Pl and P8 make at any instant an angle a with the vertical diameter or y axis of the windings of such potentiometers and the brushes 294 and 208 being 13 positioned in quadrature to the brushes 205 and 201 make at any instant the angle 90 degrees im with the vertical diameter. Therefore the potentials at the points of engagement ci the brushes 294 and 205 with the windings of potentiometer P1 are proportional to i :t sine a and :l: :r cosine a, respectively. Since the sine brush 20B of the potentiometer P3 is rotated through an angle of 180 degrees with respect to the sine brush 204 of potentiometer Pl, the sine bru n 206 leads the cosine brush 297, and therefore the potentials at the points of engagement of the brushes 205 and 29'! with the windings o potentiometer PB are proportional to i y cosine a and 1 y sine a. Hence the potential y sine a is opposite in phase to the potential a: cosine Moreover, the potential y cosine or is always equal in polarity to the potential a: sine a.

If now the sine brush 259 of potentiometer P9 and the cosine brush 295 of potentiometer Pi are connected to the input side of summing amplifier SAa, this amplier Will add the instant potentials on such brushes, l .t cosine a and a: y sine a, and will have an output potential equal to zero which will satisfy Equation 4 when the brushes have been set to a position equal to the correct value of the azimuth angle u. Also if the sine brush 294 of potentiometer Pl and the cosine brush 207 of potentiometer P8 ae*- connected to the input side of summing amplifier SArh, this amplier will add the potentials on said brushes i :r sine a and i y cosine a, and will have an output potential which will satisfy Equation 5 for the potential having a value proportional to the horizontal range rh when the brushes have been set to a position corrf-:spondingt to the value of the correct azimuth angle a.

To secure the correct value for the angle a, it is therefore only necessary to rotate the shaft 292 until such a value of angle e is attained that Equation e becomes satisiied. This is accomplished by rotating shaft 292 by a two-phase servo-motor Ma whose armature is geared to the shaft 292 through reduction gear box 238. One phase winding of the motor is energized by potential impressed upon it from the middle secondary winding of transformer T and the other phase winding is energized by potential irnpressed upon it from the output side of the summing amplifier SAa. So long as the output potential of this amplier is other than zero, the Y motor Ma will rotate in one or the other direcion and drive the shaft 2232 to change the value of the angle e until such a value is attained as `to satisfy Equation. 4 at which time the output potential'of amplifier SAO; will' become zero and the motor Ma a-.- stop. To reduce the tendency of motor Me to hunt as the output potential of ampliner Sno approaches zero and the motor slows down, the differentiating network DN shown in Fig. 5 is substituted for the feedback circuit extending' from the anode of tube DT to resistor 591.

To secure solutions for Equations 6 and 7 a pair of sine and cosine potentiometers P9 and PI9 is provided each with their brushes secured to but insulated from a shaft E03. The diametrically opposite junction points between the windings of potentiometer P9 `are connected to the end terminals of the secondary winding of transformer T5, the primary windingof which is connected across the output terminals of the summing amplier SAih. The mid-point of the secondary winding of the transformer T5 andthe mid-points of the windings of potentiometer elevation angle e.

14 P9 are eonnected'to ground. With the windings of transfo er' T5 Wound for unity transformation,

ch is proportional to the horizontal rh, is appiied to produce potentials of equal magnitude and opposite polarity at the junction ints of th gs oi potentiometer P9. The diametrically -osite junction points between the wir. oA potentiometer PHI are connected to the end terminals of the secondary Winding of transformer TS, the primary winding of which is connected across the output terminals of the summing amplifier SAS. The mid-point of the secondary winding of transformer T6 and the raid-points oi the windings of potentiometer PIU are connected to ground. With the windings of transformer T5 Wound for unit;7 transformation, the output potential from the amplifier SAe, ich is proportional to the e coordinate, is applied to produce potentials of equal magnitude and opposite polarity at the junction points of vertical diameter or y axis or the windings of such potentiometers and the brushes 209 and l Zi and Zi, rn se at any instant an angle of 90 degrees :L- E with the vertical diameter and t`-ereiore the potentials at the points of engageient or the brushes 2H and 212 with the windings entioineter Pill are proportional to i sine e and i e cosine e respectively. Since 'the sine brush 299 of potentiometer P9 is rotated throne-h an angle of 180 degrees with respect to the sine brush 2l l of potentiometer PIO, the sine brush 299 leads the cosine brush 210 and therefore the potentials at the points of engagement of the brushes 209 and 210 with the windings of potentiometer P9, are proportional to irs cosine e and im sine s.

If now the sine brush 209 of potentiometer P9 and the cosine brush 212 of potentiometer PI 0 are connected to the input side of summing amplier SA@ this amplifier will add the instant potentials on brushes. im sine e te cosine e and will have an output potential equal to zero which will satisfy Equation 6 when the brushes have been set to a position equal to the correct value of the Also if the sine brush 2H of potentiometer Pill and the cosine brush 210 of potentiometer P9 are connected to the input side of summing amplier SAT, this amplifier will add the instant potentials on said brushes, iz sine e and im cosine e, and willvhave an output potential which will vsatisfy Equation '7 for the potential having a value proportional to the slant range r when the brushes have been set to a position equal to the value of the elevation angle E.

To secure the correct value of the angle E, it is therefore only necessary to rotate the shaft 203 until the angle e attains such a value that Equation 6 becomes satisfied. This is accomplished by rotating shaft 253e by a two-phase servomotor Me Whose armature is geared to the shaft 203 through the reduction gear box 2l3. One phase Winding of the motor Me is energized by potential impressed upon it from the middle secondary winding of transformer T and the other phase winding is energized by potential impressed upon it fromv the output side of the summing amplifier' SAE. So long as the output'potential from this amplifier is other than zero, the motor Me Will rotate in one or the other direction and drive the shaft 203 to change the value of the angle e until such the output potential from the amplifier immane-22.

a value is attained as to satisfy Equation 6 at which time the output potential of amplifier SAE will become zero and the motor Me will stop. To reduce thetendency of motor Me to hunt, a dierentiating network DN is provided.

The range indicator RI is of the voltmeter type having its scale calibrated in terms of range units. Its pointer is movable over the scale in accordance with the range potential output r of the summing ampliiier SAT impressed across the voltmeter coil. It is to be understood, however, that an oscilloscope might also be used as a range indicator.

The shaft 292 carries the pair of brushes 2I/3 and 2lb of a potentiometer PI i which brushes are insulatedly positioned on the shaft 180 degrees apart so that the brush 2id makes the same angle with the vertical diameter of the potentiometer as the brushes 235 and These cru-:hes engage with the two windings oi the potentiometer which are mounted for rotation about axis or the shaft 282. For this purpose the windings may be secured to a ring gear El which may be rotated by the pinion gear 2 I '1. The two windings form a continuous circular` winding, the junction points between which being con# nected to the terminals of a battery BI, the negative terminal of which is connected to ground. The pinion gear 2H may be rotated in response to the steering control of the trainer. The potentiometer brushes 2 l Il and 2 I .5 being rotated by the shaft 232, assume a position indicative of the instant value of the azimuth angle a of the location of the No. 1 trainer with respect to the target and the windings of the potentiometer Pl I assume at any instant a position indicative of the heading oi the flight path of the No. 1 trainer. Therefore the potentials from the battery BI impressed upon the brushes 2M and 2l5 are of equal magnitude but of opposite polarity and equal to the .l Jaim and *fed-:13) it coing aslat the potential a is the poten l incident to tile pos V ."oning oi the ori the angle a and that the correction potential is the potential incident to the positioning of the windings of the potentiometer Pi I to measure the incident flight bearing angle As an alternative structure the winding of the potentiometer PlI may be made stationary and the required correction introduced by a differential gear box introduced between the shaft 282 and the brush shaft of the potentiometer with one input gear driven by shaft 2&2, the other input gear driven by the steering motor and the output shaft connested to the brush shaft of the potentiometer.

The shaft 233 carries a pair oi brushes 2I8 and 2 l Q of a potentiometer P52 insulatedly positioned on the it 1??) degrees apart so that the brufh 'MS makes the same e angle with the vertical diameter of the potentiometer as the brushes 2li? and 252. These brushes engage with the windings of the potentiometer which are mounted for rotation about the axis of the shaft 2%3. For this purpose the windings may be Secured to a ring gear 220 which may be rotated by the pinion gear 22I. rThe two windings form a continuous circular winding, the junction points between which are connected to the opposite terminals of a battery B2, the negative terminal of which is connected to ground. The pinion gear 221 may, as disclosed in Fig. 1, be rotated by the shaft which raises and lowers the horizon bar of the artificial horizon instrument of the trainer in response to the control of the trainer to simulate diving or climbing or the pinion gear 22| may be positioned by any other means responsive to the inclination of the` line of simulated flight from the horizontal. The potentiometer brushes 2I8 and 2Ii` being rotated by the shaft 233, assume a position indicative of the instant value of the elevation angle e oi the location of the No. 1 trainer with respect to the target, and the windings of the potentiometer Pl2 assume at any instant a position indicative or" the instant diving or climbing direction of the night path. Therefore the potentials impressed from the battery B2 upon the brushes 2l8 and 2&9 are of equal magnitude but of opposite polarity and are equal to the potentials v -l-(ei-w) and (eiL-J), being assumed that potential e is the potential incident to the positioning oi the brushes to measure the angle e andthat the correction potenial w is the potential incident to the positioning of the windings of the potentiometer P52 to measure the instant angle w of climb or dive. As a'n alternative construction the differential gearing previously described could be used to drive the brush shaft of the potentiometer Pi2.

'Phe potentials ziand si@ could be applied otly across the horizontal and vertical plates o the oscilloscope OSCI to control the position of ge I on the screen, indicating the locatien of the target or objective with respect to the No. i. trainer, but it is also desirable to simulate in the image position as affected by control of the trainer to simulate rolls or '.nlrs. This is accomplished by connecting the cally positioned junction points `between the windings of the sine and cosine potentiometer to produce potentials of equal magnitude ansi opposite polarity at such junction points equal to imi-). The mid-points of the windings of potentiometer PIB are connected to ground. VSimilarly the brushes of potentiometer 12.2 are connected to the diametrically positioned junction points between the windings of the sinecosine potentiometer PIllto produce potentials of equal magnitude and opposite polaritsy at such junction points equal to iol-iw). The midpoints of the windings of potentiometer PM are connected to ground. The sine and cosine brushes 222 and 22S of potentiometer P 5'3 and the eine and cosine brushes 22d and 225 of potentiometer PM are insulatedly mounted on the shaft 22S which shaft controls the articial horizon instrument of the trainer to indicate simulated roll or bank or the shaft 226 may be The sine brush 224 of potentiometer PIl and the cosine brush 223 of potentiometer P13 are c nected to the input side of a summing amplidei SAM, the output side of which is bridged across the horizontal plates of the target location oscilloscope OSCI. The sine brush 22?! of potention'ieter P93 and the cosine brush 225 of potentiometer PM are connected to the input of a summing amplier SAec, the output side rich is bridged across the vertical plates of the oscilloscope OSCI. If at any instant it be assumed that the angle of roll with respect to rtical axis of the potentiometers may be ented by then summing ampliier SAae wil add the instant potentials on brushes 224 and fisio) sine and this) cosine and summing amplifier SAeG will add the instan potentials 'on brushes 222 and 225 ifa-rf?) sine and -(etw) cosine 6.

If there is no roll and consequently the angle I aurais 17 is zero, then the potential iieiw) sine on lbrush 224 becomes zero and the potential iwi/3) cosine on brush 223 becomes inzio) and consequently the output potential from the summing ampliiier SAM .becomes ibxi). Also the potential itai) sine on brush 222 be- 18 gun lead, the` vanes may be mechanically biased as .by a biasing spring or electrically biased as by the addition of a biasing Winding.

Relay 223 is normally held operated over the nor- SAac and SAGC as to make the target image rotate in a circular path about the axis of the oscilloscope screen.

At any instant, therefore, the image spot I on the screen of location oscilloscope OSCI indicates the general bearing of the target or objective with respect to tlrie location of the No. 1 trainer. If now the trainee operates the steering controls of the trainer thereby causing the rotation of the winding of potentiometer PII until the angle becomes equal to the angle a. at

which time the heading of the trainer will be -in the direction of the horizontal range Th as indicated in Fig. 4, then the output poteiitials from the potentiometer PII will vbecome Zero and consequently the potential applied from the amplifier SAM to the horizontal plates of the oscillcscope OSCI will become zero and the image I will move into a position along the' vertical cross-hair on the screen of such oscilloscope. If the trainee also operates the elevator controls of the trainer and thereby causes the rotation of the windings of potentiometer Pl'2 until the angle s becomes equal to the angle e, at which time the heading of the trainer will be in the direction of the slant range r as 'indicated in Fig.4 4, then the output potentials from the potentiometer PIE will become zero and consequently the potential applied from the amplifier SAes to the vertical plates of the oscilloscope OSCI will be'- come zero and the image I will moveinto a position at the intersection of the' cross-hairs of the oscilloscope screen. In an aircraft equipped with radio location equipment, this would be the correct instant toy iire the xed gun carried by the aircraft since at only this instant would the gun be trained upon the target whose' image ap'- pears on the screen of theradio locator;

To simulate the eiTect oi firing the gut;` underA this condition two relays 221 and 228 of the volt.. meter type are provided, relayr 2217 having its winding bridged across the vertical plates of the oscilloscope OSCI and energizable b'y the potential appied across such plates from the amplifier SAE@ and relay 228 having its winding bridged across the horizontal plates of the oscilloscope and energizable by the potential applied across such plates from the amplifier SAM.l The varies or armatures of these relays are connected to ground and the front and back contacts of both relays are connected together and to the winding of a third relay 229. Relays 221 and 228 are both so adjusted that their vanes will be positioned mid-way betweenA their associated fron-t and back contacts and out of engagement therewith only when the output potentials from the amplifiers are such as to position thef image' spot I at the center of the screen of the oscilloscope or of zero values. Should itbe desired to cause the varies of both relays tof be out of engagement with their associated contacts at some point other than the center, for example by an amount representing mally closed contacts of key TR and over a front or back contact of one or both of the voltmeter relays 227 and 228. If however, key TR Which corresponds to a gun release trigger, is depressed at the instant -the target image I is at the center of the screen of the oscilloscope, the relay 229 will have no holding circuit and will release to apply a short-circuiting ground to the path over which the e2 input potential is received by the summing amplifier SA?.l from the altimeter potentiometer PS ci' the No. 2 or target trainer.`

The removal of the Z2 input potential from the Siae summing amplifier will so change the output potential or" the amplier SAe that the servo-motor Me will be operated to determine ya new value for the sigle e which will again satisfy Equation 6. Potentiometer PE2 is thereupon operated to produce new potentials at its brushes of such a value as to depress the position of the image I of the target on the screen of oscilloscope OSCI to indicate the traget as having been hit and falling. At the same time, the operation of the servo-motor Ms changes the value of the output potential of the amplifier SAT to control the range indicator Ri to indicate a changed range. The rate at which the target appears to fall is determined by the followup speed of the servo-motor Me. This may be reduced by inserting an attenuating pad inl the motor circuit by contacts closed when relay 229 operates. A contact may also be added to relay 229 to break the power circuit to th'e trainer No.

2 when a hit has been secured by the No. 1 trainee to represent the annihilation of the target.

Obviously a second oscilloscope and range indicator similar to OSC! and Ri may be located in the No. 2 trainer together with another set or potentiometers PII, PE2, PIS and PI4 to operate such Oscilloscopes. These potentiometers as in the No. l trainer may be driven in' accordance with the direction of steering and the bank and pitch of the artificial horizon instrument of the No'. 2 trainer. Ir this case the brushes of the Pil and PI 2 potentiometer-s of the No. 2 trainer should be displaced 180 degrees from those of the No. l trainer. Relays similar to relays 221, 228- and 229 and a key similar to key TR lmay be provided in the No. 2 trainer to enable its trainee to simulate' the securing of a hit on the No. 1 trainer.

If desired, sound and vibration effects correspending to those of gun-'nre may be introduced through the operation of thev trigger release key TR and a timing circuit could be added limiting the length of time the gun may be recl simulating the expenditure of ammunition. The

sound eects circuit is represented by rectangle and the vibration effects circuit is represented by the rectangle 243 shown in Fig. 2 and are controlled by the contacts of key TR. The vibration circuit'would include the vibration magnet B diagrammatically illustrated in Fig. 8.

In lieu of the equipment disclosed to' simulate two airplanes in flight, xed voltages may' be introduce-d at the inputs of the ampliers SA, SAQ; and SAeg replacing the r2', y2 and ez potentials from the second trainer to thus simulate stationery objects in the air or on the` ground, or the potentials rz and' yz may bevaried with the potential .e2 made equal to zero to' simulate a ship at sea or an object moving onthe ground.

Referring now to Figs. 6 and 'l which disclose a further modication of the invention, it will be assumed that two trainers are to be employed for training aircraft personnel and that the iirst trainer, identied as trainer No. l, is provided with the control equipment, location oscilloscope OSCI, range meter' Ri and potentiometers Pili and Pil) disclosed in the left portion of these figures, that the second trainer, identified as trainer No. 2, is provided with the control equipment, location oscilloscope OSCE, range meter Rz and potentiometers P28 and P25 disclosed in the right portion of these iigures and that the apparatus disclosed in the central portion of these figures is equipment common to both trainers. The brush shaft Si of potentiometer PiE is driven by the motor of the No. l trainer which drives the air speed indicator thereof, or it may be operated by any other means responsive to the simulated air speed, and the winding of e put potential Asi from the ampliiier Adi is'mpressed upon the primary winding of transformer T8, the end terminals of the secondary winding of which are connected to the junction points between tlie windings of the sine-cosine potentiometer P46.

The mid-point of the secondary winding of transformer T8 and the mid-points or" the windings of the potentiometer Pit are connected to ground. With the windings or" this transformer wound for unity transformation, the potential derived by the position of brush till is applied to produce potentials of equal magnitude and opposite polarities at the junction points of the windings of potentiometer Pl for exciting such windings. The brushes 632 and tlS of potentiometer Pl are mounted on shaft GEIE which may be driven by the motor on the trainer which raises or lowers the horizon bar or the artificial horizon instrument or operates the rate of climb indicator responsive -to the inclination of the path of the simulated flight from the horizontal and therefore the angle er between the brush 653 and the y axis of such potentiometer is always proportional to the angle of climb or dive of the simulated flight. As the brushes of potentiometer P 5,5 move over the windings of such potentiometer the potential Asi applied to its windings is fractionated in accordance with the angular position ei of the brush i533, the potentials resulting at the points of engagement of the brushes S612 and 603 with the windings being proportional to the zo and hr coordinates of the flight position of the No- 1 trainer and may be expressed as The potential Asie@ is impressed upon the input circuit of ampliiier Asi and the potential Asrh is impressed through the decoupling amplier Ads upon the primary winding of transformer T9, and the end terminals of the secondary winding of which are connected to the junction points between the windings of the sine-cosine potentiometer Pl'l. The mid-point of the secondary windings of transformer TQ and the midpoints of the windings of potentiometer PI'I are connected to ground. With the windings of the winding 663.

20 transformer 'Ti-l wound for unity transformation. the potential Asili produces potentials at the junction points of the windings of potentiometer P l 'l for exciting such windings or equal magnitude and opposite polaritles. The brushes 3135 and 66 of potentiometer Pil are mounted on shaft 'l, which may be driven by the motor of the trainer which operates the compass in response to the horizontal steering control. Therefore the angle i between the brush 5&5 and the y axis of the potentiometer Pil' is always proportional to the azimuth angle of the night heading. As the brushes of potentiometer PI'I move over the windings of such potentiometer the potentialsAsih applied to its windings is fractionated in accordance with the angular position ai of the brush 5F35, the potentials resulting at the points of engagement of the brushes i595 and S08 with the windings of the potentiometer PI 'i being proportional to the VX and Vy velocity components of the flight along the and y axes respectively of the Nlo. l trainer and may be expressed as The potentials Vx and Vy are impressed upon the input circuits of amplifiers exi and Ayr.. The output circuit ol' amplifier Arr is connected with the control winding or the two-phase motor M331 of motor-generator set serving as an integrator. The other phase winding of the motor Mri and one phase Winding of the coupled generator Gar; are energized from the alternating current source AC through the windings of transformer T7. The other phase winding of the generator Gi is connected to the feedback circuit of the amplifier Ari. The output circuits of the amplifiers Ayr and Aer are similarly connected to the control phase windings o motors My; and Mei of the associated integrators, the output phase windings of the generators Gyi and Gar of such integrators being similarly connected to the feedback circuits of the amplifiers Ayr and A21.

The shaft Stil of motor M31 drives the brush 555 of potentiometer P35 through gear reduction boX $52. The winding i333 of potentiometer P36 is energized from the secondary winding of transformer Tl in such manner that opposite potentials are applied to the opposite ends of said Brush 66| is moved over winding 663 in accordance with the speed and time interval during which motor Mr; is operated by the potentials impressed on amplifier Ari. Accordingly, brush S65 selects a potential from the winding 553 proportional' to the time integral of the potential from brush G of potentiometer PH which is the integral of the function Asrh sine X1=V1, and therefore represents the change in coordinate of the ight during the given time interval. The potential of brush 55E at any instant is indicative of the rr coordinate of the flight path at that instant. This potential is impressed on summing amplier Sax. In like manner potentials -yr, and 211, are impressed upon the input circuits oi the simnninfT ampliers SAy and SAz from potentiometer-s P37 and P38 operated from integrator motors Myi and Msi respectively. The function of the integrators is to change the potentials impressed upon the arnpliers Afri, Arr and A21 which vary in accordance with the air speed or velocity into potentials impressed upon the summing ampliers which shall vary in accordance with the coordinates of the position of the trainer in its simulated night.

Other well-known types of integrators could be employed. For example, the circuits incoming to the amplifiers Ai, Ayi and A21 could be connected to the driving coils of wattmeters, the rotors of which are employed to drive brushes over the windings oi potentiometers energized by alternating current, such brushes being connected to the input circuits of the summing ampliers to impress potentials thereon varying with respect to the input potentials A-siro, -Asiyo and -Asiza Similarly, with respect to the No. 2- trainer assumed to be conducting a simulated flight over the same terrain, the potentiometer 5 is supplied with potential from the source AC through the windings of power transformer Til and the brush shaft 655i! thereof is driven by the motor of the trainer which drives the air speed indicator. In response, therefore, to changes in the air speed of the simulated flight a potential is applied over the brush 65! of potentiometer P253 to the input circuit of the decoupling amplifier Ada. The output potential Ass from the amplifier Ade is impressed upon the primary winding of transformer TIB the end terminals of the secondary winding of which are connected to the junction points between the windings of the sine-cosine potentiometer P26.

The mid-point of the secondary winding of transformer TlS and the mid-points of the windings of the potentiometer P25 are connected to ground. With-the windings of the transformer wound for unity transformation the potential derived by the position of brush 65d is applied to' produce potentials oiequal magnitude and opposite polarities at the junction points of the windings of potentiometer P25 for exciting such windings. The brushes 652 and 553 of potentiometer P26 are mounted on the shaft 555i which may be driven by the motor of the trainer which raises and lowers the horizon bar of the articial horizon instrument of the trainerl or which operates the rate of climb indicator and therefore the angle e2 between the brush and the y axis of such potentiometer is proportional to the angle of climb or dive of the simulated flight. As the brushes of potentiometer P252? move the potential Ass applied to the windings of such potentiometer is fractionated in accordance with the angular position ez of the brush the potentials resulting at the points of engagement of the brushes 852 and 653 with the windings of The potential Asze'c is impressed upon the input circuit of the amplifier Aez and the potential A3271. is impressed through the decoupling emplier Ad4 upon the primary winding of transformer T39, the end terminals of the secondary winding of which are connected to the junction points between the windings of the sine-cosine potentiometer P21. The mid-point of the secondary winding of transformer Til and the mid-points of the windings of potentiometer P2? are connected to ground. With the windings of transformer T19 wound for unity transformation the potential Aszh produces potentials at the junction points of the windings of potentiometer P21 for exciting such windings which are of equal magnitude and opposite polarity. The brushes 655 and 656 of potentiometer P27 are mounted on shaft 651 which may be driven by the motor 22 of the trainer which operates the compass in' re sponse to the horizontal steering control. Therefore, the angle a2 between the brush 655 and the y axis of the potentiometer is always proportional to the azimuth angle of the flight course. As the brushes of the potentiometer P27 move the potential Aszh applied to its windings is fractionated inaccordance with the angular position a2 of' the brush G55, the potentials resulting at i A be expressed as As2u=As2h sine a2 (11) As2yo=As2h cosine a2 The potentials Asemo and Aszyo are impressed upon the input circuits of the ampliers Awa and Aya, The output potentials from the ampliers Azra and Aya and Azz are integrated by the motorgenerator sets MxsGxz, MyzGi-'z and l-.fleeGeg and the potentioineters Pla, Pi? and P58 are impressed upon the inputs of the summing ampliers SA, SAU and SAZ potentials cs2, y2 and e2. The resultant potentials derived from the surnming ampliiiers being the sums of the potentials impressed upon their input circuits, result in the potentials in accordance with the following equations :E2-:E1=:L (12) y2y1=y 22-21=Z The output potentials from summing amplifiers SAQ: and SAg/ are impressed through the transformers T90 and TH across the junction points between the windings of the sine-cosine potentiometers PS2 and P33, are fractionated thereby and impressed upon the summing amplifiers SArh and SAa whereby a potential is derived from the amplier SAa for driving the motor Ma which, through, the reduction gear box E08, positions the brushes 5tlg and E l0 oi potentiometer PS2 and brushes Ell and 612 of -potentiometer P33 until the brushes tilg and 6H assume positions with respect to the y axes of such potentiometers in which such a value of the angle a is obtained as will satisfy Equation 4 as fully described in connection with the modification disclosed in Fig. 2. At such time the input shaft BIS of the differential gear box 6H! will have been rotated by the motor` Ma to a position indicative of the correct azimuth angle a of the iglit path which the No. 1 trainer must ily to reachv the No. 2 trainer and since the shaft 6l@ is connected by gearing SI5, shaft 6 i 5 and gearing 6H with the input shaft BIB of diierential gear box SiS the shaft 618 will be rotated an equal amount but will assunte a; angular position corresponding to the value a-l-lSO, At the same time the output potential from the summing amplifier SArh will have a value proportional to the horizontal range rh between the assumed ight positions of the two trainers. This potential is now applied through the windings of transformer T43 across the junction points between the windings of sine-cosine potentiometer P35 and with the coordinate potential .e applied from the summing aplier SAz through the winding of transformer T12 across the junction points between the windings of sine-cosine potentiometer P34. Such potentials are fractionated by the potentiometersPA and P35 and impressed upon the summing amplifiers SAT and SAE whereby a potential is derived from the amplifier SAe for driving the motor lMe which through the 'li 'IIE the shaft iil will be rotated an 23 reduction gear box '160 positions the brushes 'IBI and 102 of potentiometer P3@ and brushes 753 and '104 of potentiometer' P35 until the brushes 'IGI and iBS assume positions with respectl to the y axes of such potentiometers in Which such a value of the angie is tion 6 as fully described in connection with the modification disclosed in Fig. 2. At such time the input shaft ci the diierential gear box 106 will have been rotated by the motor Me to a position indicative of the correctv elevation angle e of the flight path ivi 1 tr incr in si. fly to reach the -o. 2 train shaft HS is connected by gearing 'is st and gearing '39 with the input shaft il ci differential gear box amount -on corresponding but will assumo an angulo. to the value e-i- 180.

At the same time the output potential from the summing amplifier Snr will have a value proportional to the slant range?- or the actual distance between the flight positions of the two trainers. This potential is applied tothe coils of the two range meters Ri and R2 associated respectively With the tWo trainers and, with the scales of these meters calibrated in tern-1s of range, each trainee who is operating one of the trainerspiay at any instant determine the distance from his trainer to the other tr iner.

The other input shaft E20 of the dilerential gear box 514 is connecte-:l through ing 62! to the shaft 6ST which, as previously described, is driven by the steering motor and thus at any instant assumes a positon indicative of the bearing of the simulated night f the No. 1 trainer. The dierential gear box 5M is thus driven by the shafts SIS and 525.3 so that the output shaft 522 assumes a position corresponding to the azimuth angle o. corrected by the instant value of the steering or yawing angie ai or mia, which ,t

may be termed ci correspondingly positions the brush Q23 of the potentiometer PS3. Similarly the other input shaft @-4 of dilerential gear box @i9 is connecter thr ugh gearing 525 to the shaft 557 which, as previously described is driven by the steering motor of the No. 2 trainer and thus at any instant assumes a position indicative of the bearing of the simulated ilight of the No. 2 trainer. The differential gear box 619 is thus driven by the sha; s Gli? and 52d so that the output shaft assumis a position corresponding to the a 393 corr-ted by the instant vai t en e as or aat (a--l80) which may be termed /32 and correspondingly positions the br the potentiometer i 2- With f" potentiometcrs Pili and P25 ing current source AC potentials are derived at the brushes and 827 of such potentiometers having the values ici and iz which include corrections for the yawing of the trainers in their simulated flights.

The other input shaft 'H2 or" the differential gear box 'illi is connected through gearing 'H3 to the shaft E94 which, as previously described, is driven bythe motor which raises or lowers the horizon bar of the artilcial horizon instrument of the No. 1 trainer and thus at any instant assumes a position indicative of tite angle of pitch of such trainer. The diersntialgeac bof; is thus driven by the shafts "55 and 'H2 so that the output shaft 1U.; assumes a position corresponding to the elevation angle e corrected by the instant value of the angle ci pitch si or site which may be termed wi and correspondingly e 24 positions the brush I 5 of the potentiometer PIB'. Similarly, the other input shaft 'i i 5 of diierential gear box Il i is connected through gearing I II tov -ie rlmit $551 which, as previously described, is dri ..1 by the niotoiufhich raises or lowers the horizon bar of the articial horizon instrument of No.2 trainer and thus at any instant assumes a position indicative of the angle of pitch oi such trainer. The differential gear box III is' thus driven by the shafts 'Iiil and IS so that he output shaft 'H8 assumes a position correspending to the elevation angle e corrected bythe instant value or" the angle of pitch e2 or esi-(s+ 180) which may be termed ws and correspondingly positions the brush 'H9 of the potentiometer P29. With the windings of potentiometers P l 3 and energized Toy the source of alternatng current AC potentials are derived at the brushes 'H5 and 'Il of such potentioineters havvalues iwi and im which include corf i'or the pitching oi" the trainers in their mulated flights.

rihe potentials ,Bi and wi and [i2 and wz could be applied directly across the horizontal and vertical plates of the oscilloscope OSC and OSCZ, ively to control the positions of the images and if; on the screens indicating the location of each trainer With respect to the other but it is also desirable to simulate the change in the image position as aiected by the control of the trainers to simulate rolls or banks. This is accomplished With respect to the No. l trainer by connecting the brush J323 of potentiometer PIB own. in Fig. 6 and brush H of potentiometer of Fig. 7 to the input circuits of amplifiers ai and A3, the output circuits oi which amplifiers are connected to the primary windings of transformers Tit and Ti. The end terminals of the secondary of transformers TI4 and TI5 are connected to the junction points between the windings of the sine-cosine potentiometers P20 and 132i. The transformers have unity transforinaticn and the mid-points ci their secondary windings and the mid-points of the windings of the pctentiornetersPZil and P2I are connected to ground. The brushes 72B and 72E of potentiometer and the brushes 22 and T23 of potentiometer P25 are mounted on the same shaft 724 which may be turned by the motor which controls the tilting of the horizon bar of the artificial horizon. instrument of the trainer. At any instant the brushes 'II and 'i222 will assume a position with respect to the y axes of the potentiometers equal to the angle of roll 5i.

The movement of he brushes of potentiometers P263 and PEI fractionates the input potentials i and o1 and applies the instant potentials on brushes '528 and '5251, iwi sine i and i cosine 6i upon the input circuit of summing amplier Salat and such amplifier will add these potentials and apply the result through the modulator vii across the horizontal plates of the oscilloscope OSCi. At the same time the instant poten- 'tials of brushes li and '123, ii sine i and iwi cosine 61 are applied upon the input circuit of summer amplifier SAieC and such amplifiers will add these potentials and apply the result through the modulator across the vertical plates of the oscilloscope OSCI.

At any instant therefore the image spot I1 on the screen of location oscilloscope OSCI indi- Cates the bearing of the flight position of the No. 2 trainer with respect to the flight position of the No. 1 trainer. If now the trainee operates the steering controls of the trainer until the location equipment this would be the instant .to i

re a nxed gun carried by the aircraft since only at this instant would the gun be trained upon the target whose image appears on the screen of the radio locator.

Similarly the potentials ,82 and wz derived at l0 the brushes 627 and 'i I9 of potentiometers P28 and P25 are applied to the input circuits of amplifiers A2 and All, the output circuits of which ampliiiers are connected to the primary windings of transformers T2A and T25.

and T25 are connected to the junction points between the windings of the sine-cosine potentiometers P35 and P3 l. These transformers have The end terminals vof the secondary windings of transformers T2ri unity transformation and the mid-points of their tiometer P3! are mounted on the same shaft 12S 25 which may be turned by the motor which controls.

the tilting of the horizon bar of the artificial horizon instrument of the No. 2 trainer. At any instant the brushes 726 and 121 Will assume a position with respect to the y axes of the potentozneters equal to the angle of roll 52.

The movement of the brushes of the potentiometers P and P31 fractionates the input potentials ,82 and wz and applies the instant potentials on brushes l25 and 121, im sine 52 and i131 cosine t2 upon the input circuit of summing amplier SAmc and such amplifier will add these potentials and apply the result through the modulator M2 across the horizontal plates of the oscilloscope OSC?. At the same time the instant potentials on brushes and 128 ifi; sine 62 and iwi cosine 62 are applied upon the input circuit of summing amplifier SAgec and such amplifier will add these potentials and .apply the result through the modulator M-t across the vertical plates of the oscilloscope OSCE.

At any instant therefore the image spot I2 on the screen of location oscilloscope OSCZ indi- 'caters the general bearing of the night position of the No. l trainer with respect to the iiight position of the No. 2 trainer. If now the trainee operates the steering controls of the trainer until the image spot I2 becomes centered on the screen of the oscilloscope the No. 2 trainer would be flying a simulated course directly toward the No. 1 trainer.

Apparatus for simulating the firing of a gun carried by either trainer when the trainer is flying a course directly toward the other trainer, has been omitted from Fig. 7 but apparatus similar to that disclosed in Fig. 2 or other equivalent apparatus could be used equally well with the apparat-us of Fig` '7` While the system disclosed in Figs. 6 and 7 is shown as operating on alternating current it would be equally operable on direct current by replacing the transformers with reversing am-. plifiers. In the alternating current system disclosed in Figs. 6 and 7 the sine-cosine potentiometers could be replaced by magnetic resolvers of the well-known type.

What is claimed is:

l. In an aircraft trainer operable by a trainee in simulation of flight, means for determining the instant values of the Cartesian 'coordinates of 26 the simulated changing position of the trainer in its simulated flight, means for determining the values of the Cartesian coordinates of the simulated position of a simulated objective, means for combining said coordinates and resolving the results into potentials representative of the distance and azimuth and elevation angles of the path from the simulated flight position of the trainer to the objective, and indicating means operable in response to the distance and azimuth and elevation angle potentials to indicate the instant distance to the objective and the instant position of the objective with respect to the simulated line of night of the trainer.

2. In an aircraft trainer operable by a. trainee in simulation of night, means for determining the instant values of the Cartesian coordinates of the simulated changing position of the trainer inits simulated ight, means for determining the values of the Cartesian coordizfiates of the simulated position of a. simulated objective, means for combining said coordinates and resolving the results into potentials representative of the distance and azimuth and elevation angles of a path from the simulated flight position of the trainer to the objective, a rst indicator operable in response to said distance potential to indicate the instant distance to the objective, and a second indicator operable in response to the azimuth and eleva.- tion angle potentials to indicate the instant position of the objective With respect to the line of simulated night of the trainer.

3. In an aircraft trainer operable by a trainee in simulation of flight, means for determining the instant values of the Cartesian coordinates of the simulated changing position of the trainer in its simulated flight, means for determining the values of the Cartesian coordinates of the simulated position of a simulated objective, means for combining said coordinates and resolving the results into potentials representative of the dise tance and azimuth and elevation angles of a path from the simulated flight position of the trainer to the objective, a first indicator operable in response to said distance potential to indicate the instant distance to the objective, a second indicator operable in response to the azimuth and elevation angle potentials to indicate the instant position of' the objective with respect to the line of simulated flight of the trainer, and means to modify the operation of said second indicator in response to the simulated deviation of the trainer .from straight line flight.

4. In an aircraft trainer operable by a trainee in simulation of ight, means for determining the instant values of the Cartesian coordinates of the simulated changing position of the trainer in its simulated night, means for determining the values of the Cartesian coordinates of the simulated position of a simulated target, means for combining said coordinates and resolving the results into potentials representative of the djstance and azimuth and elevation angles of a path. from the simulated flight position of the trainer to the target, a rst indicator operable in response to said range potential to indicate the instant range, a second indicator having a screen operable in response to the azimuth and elevation angle potentials to indicate the instant position s of the target with respect to the line of simulated T 0nd indicator to alter the vertical coordinate ,of

27 1 said result whereby the target position on the screen of said second indicator is depressed to indicate the target as hit and falling.

5. In an aircraft trainer operable by a trainee in simulation of flight, means for determining the instant values of the Cartesian coordinates of the simulatedchanging position of the trainer in its. simulated flight, means for determining the instant values of the Cartesian coordinates of the simulated changing position of a moving objective, means for combining said coordinates and resolving the results into potentials representative of the distance and azimuth and elevation angles of a path from the simulated flight position of the trainer to the objective, a first indicator operable in response to said distance potential to indicate the instant distance to the objective and a second indicator operable in response to the azimuth and elevation angle potentials to indicate the instant position of the objective with respect 2J to the line of simulated flight of the trainer.

6. In combinaion, a first aircraft trainer operable by a first trainee in simulation of flight, means for determining the instant Values of the Cartesian coordinates ofthe simulated changing position of the trainer in its simulated flight, a second aircraft trainer, operable by a second"- tra'inee in simulation of flight, means for determining the instant values of the Cartesian coordinates of the simulated changing position of said o second trainer in its simulated flight, means for combining said coordinates and resolving the results into potentials representative of the range and azimuth and elevation angles of the path, from the simulated flight position of the first 3;,

trainer to the simulated flight position of the second trainer, a first indicator operable in re. sponse to said range potential to indicate the instant range between the flight positions and a second indicator operable in response to the indicated azimuth and location angle potentials o indicate the instant flight position of the second trainer with respect to the line of simulated flight of said ilrst trainer,

'7. In combination, a first aircraft trainer operable by a first trainee in simulation of flight, means for determining the instant values of the Cartesian coordinates of the simulatedchanging position of the trainer in its simulated flight, a second aircraft-trainer, operable by a second trainee therein in simulation of flight, means for determining the instant values of the Cartesian coordinates of the simulated changing position of the second trainer in its simulated flight, means for combining said coordinates and resi' solving the results into potentials representative of the range and azimuth and elevation angles of the path between the simulated flight position of the first trainer and the simulated flight po sition of the second trainer, and means operated in response to said range and azimuthand elevation angle potentials to indicate the range between the flight positions of said trainers and to indicate the flight position of each trainer with respect to the other trainer. 05

8. An aircraft trainer operable by a trainee in simulation of flight, means for determining the instant values of the Cartesian coordinates of the simulated changing position of the trainer in simulated flight, means for determining the values of the Cartesian coordinates of the simulated position of an objective, means for coinbining said coordinates and resolving the results into potentials representative of the distance and azimuth and elevation angles of a ilight path 255 from the simulated flight position of the trainer to the objective, a rst indicator operable in response to the distance potential to indicate the distance` a second indicator operable in response to the azimuth and elevation angle potentials to indicate the position of the objective with respect to the line of simulated flight of the trainer, and means to modify the operation of said second indicator in response to the simulated deviation of the trainer from straight line flight.

9. In combination, a first aircraft trainer operable by a rst trainee in simulation of flight, means for determining the instant values of the Cartesian coordinates of the simulated changing position of the trainer in its simulated flight, a second aircraft trainer, operable by a second trainee in simulation of flight, means for determining the instant values of the Cartesian coordinates of the simulated changing position of said second trainer in its simulated flight, means for combining said coordinates and resolving the results into potentials representative of the range and azimuth and elevation angles of the path from the simulated flight position of the rst trainer to the simulated flight position of the second trainer, means associated with each of said trainers operable in response to said range and azimuth and elevation angle potentials to indicate the range between the flight positions of said trainers and to indicate the flight position of each trainer with respect to the other trainer, and means to modify the operation of said indicating means lnvresponse to the simulated deviation of the trainers from straight line flight.

l0. In combination, a first aircraft trainer operable by a first trainee in simulation of flight, means for determining the instant values of the Cartesian coordinates of the simulated changing position of the` trainer in its simulated fiight, a second aircraft trainer, operable by a second trainee in simulation of flight, means for determining the instant values of the Cartesian coordinates of the simulated changing position of said second trainer in its simulated flight, means for combining said coordinates and resolving the results into potentials representative of the range and azimuth and elevation angles of the path from the simulated flight position of the first trainer to the simulated flight position of the second trainer, a first indicator associated With each trainer operable in response to the range potential to indicate the distance between the flight positions of said trainers, a second indicator associated with each trainer operable in f response to the azimuth and elevation angle potentials to indicatel the flight position of the other trainer with respect to the flight position of the trainer With which the latter indicator is associated, and means for modifying the operation of the second indicator of each trainer in response to the simulated deviation of such trainer from straight line flight.

11. In an aircraft trainer operable by a trainee in simulation of flight, means for determining the instant values of the Cartesian coordinates of the simulated changing position of the trainer in simulated flight, means for determining the values of the Cartesian coordinates of the simulated position of an objective, means for combining said coordinates and resolving the results into potentials representative of the distance and azimuth and elevation angles of a flight path from the simulated flight position of the trainer to the objective, a ilrst indicator operable in response to the distance potential to indicate th instant 

